This invention relates to electric power systems and, more particularly, to a solar electric system having capacitive energy storage in a painted layer.
Solar energy is generated in space and terrestrial applications by a solar electric system that includes a solar cell which generates power, an energy storage device in the form of a battery system, and appropriate electrical connections to the load. The batteries are typically required because solar energy generation by the solar cell is intermittent and subject to interruptions due to periods of eclipse and spacecraft orientation in space applications, and clouds and nightfall in terrestrial applications. The solar cell generates power when it is in sunlight. Some of the power is used immediately and the remainder charges the batteries. When the solar cell is not producing an output or extra energy is needed in addition to the current production of the solar cell, the power is supplied by the discharging of the batteries.
The battery system ordinarily includes a number of batteries interconnected appropriately to provide the required voltage and current output. The batteries available today are, despite extensive research and development, relatively bulky and heavy. The batteries for use in space applications must be designed for high reliability to meet spacecraft design lives, which may be 15 years or longer for geosynchronous communications satellites. The individual batteries are nevertheless subject to failure and eventual exhaustion, and to operational and regulation problems. The battery system therefore includes circuitry for monitoring and carefully controlling the batteries, and for bypassing batteries that fail during service. The battery system used for energy storage in the solar electrical system, which includes both the batteries themselves and their monitoring and control circuitry, is bulky, heavy, and complex.
There is an ongoing need for an improved approach to energy storage in solar electric systems. The present invention fulfills this need, and further provides related advantages.
The present invention provides an electric power system in which energy storage is provided in whole or in part by a paint capacitor. The capacitor is preferably integral with a voltage source such as a solar cell, or it may be separate from the voltage source. The capacitor is inexpensive to fabricate, and it is light in weight, adds little volume, and is robust. The capacitor may be designed to completely replace the batteries or, more typically, supplements the energy storage in the batteries so that the required size and weight of the batteries may be reduced. The preferred application of the paint capacitive energy storage is with a solar cell, but it may be used with other types of voltage sources as well.
In accordance with the invention, an electric power system comprises a voltage source structure of any operable type, but preferably a solar cell; an electrical conductor structure comprising a first electrically conductive contact to the voltage source structure and a second electrically conductive contact to the voltage source structure; and a capacitor in electrical communication with the second electrically conductive contact. The capacitor includes a capacitive paint layer structure comprising capacitive pigment particles, preferably pyroelectric/ferroelectric pigment particles, dispersed in a capacitive layer binder. Most preferably, the pyroelectric/ferroelectric pigment particles are ferroelectric pigment particles. The binder may be inorganic or organic. The capacitive paint layer structure may further include filler particles. A first side of the capacitive paint layer structure is in electrical communication with the second electrically conductive contact, and preferably is painted upon the second electrically conductive contact. The capacitor further includes a capacitor electrically conductive contact in electrical communication with a second side of the capacitive paint layer structure remote from the first side. A battery may be electrically interconnected with the capacitor.
The electric power system is prepared by providing a voltage source structure having a first electrically conductive contact and a second electrically conductive contact, and preparing a flowable capacitive paint comprising pyroelectric/ferroelectric pigment particles, a capacitive layer binder, and a capacitive layer vehicle. The electric power system is fabricated by applying a layer of the flowable capacitive paint to the second electrically conductive contact, drying the flowable capacitive paint to form a capacitive paint layer structure having a first side of the capacitive paint layer structure in electrical communication with the second electrically conductive contact and a second side remote from the first side, and applying a capacitor electrically conductive contact to the second side of the capacitive paint layer structure.
The capacitive paint stores electrical energy generated by the voltage source structure and may be later discharged through the load when the electrical energy is needed. The capacitive paint allows the heavy, expensive electrical storage batteries to be reduced in number and size, or eliminated completely from the electrical system.
The paint capacitor is ideally suited for use with solar cells and other types of voltage source structures that require a relatively large area for the production of electric power. The paint capacitor is applied as a layer to the back side of the solar cell away from the sun-facing side. The back side of the solar cell otherwise has only the function of providing one of the electrical contacts to the solar cell voltage source.
The present invention provides a major advance in the art of electrical power sources and particularly in regard to solar cells and photovoltaic generation of electrical power. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.